Cauliflower Gratin

1. FOR THE TOPPING: Pulse bread, butter, salt, and pepper in food processor until mixture resembles coarse crumbs, about 10 pulses; set aside.
2. FOR THE FILLING: Adjust oven rack to middle position and heat oven to 450 degrees. Bring 4 quarts water to boil in Dutch oven over high heat. Add cauliflower and 1 tablespoon salt and cook until just tender, 3 to 4 minutes. Drain cauliflower in colander and rinse under cold water until no longer hot. Leave cauliflower in colander to drain while preparing sauce.
3. Melt butter in 12-inch skillet over medium heat, add shallot, and cook until softened, about 2 minutes. Add garlic and cook until fragrant, about 30 seconds. Stir in flour until combined, about 1 minute. Whisk in cream and bring to boil. Stir in 1⁄2 cup Parmesan, thyme, remaining 1⁄4 teaspoon salt, pepper, nutmeg, and cayenne until incorporated. Off heat, gently stir in cauliflower until evenly combined. Transfer mixture to 11 by 7-inch (2-quart) gratin dish. Sprinkle remaining 2 tablespoons Parmesan evenly over surface, then sprinkle evenly with bread-crumb topping. Bake until golden brown and sauce is bubbling around edges, 10 to 12 minutes. Serve immediately.
   TO MAKE AHEAD: Topping and cauliflower can be prepared and stored at room temperature for up to 2 hours. Don’t prepare sauce or bake gratin until just before serving.

CAULIFLOWER GRATIN WITH LEEKS AND GRUYÈRE
Add 1 pound leeks, white and light green parts only, halved lengthwise, sliced 1⁄4-inch thick, and washed thoroughly, to skillet with shallot in step 3 and increase cooking time to about 4 minutes, until leeks are softened. Substitute 2 ounces Gruyère cheese, grated (1⁄2 cup), plus 2 tablespoons, for the Parmesan.

CAULIFLOWER GRATIN WITH HAM AND CHEDDAR CHEESE
Add 6 ounces ham steak, cut into 1⁄2-inch cubes, to skillet with shallot in step 3. Substitute 2 ounces cheddar cheese, grated (1⁄2 cup), plus 2 tablespoons, for the Parmesan.